The present invention relates to improvements in book binding machines and in particular to book bindings incorporating flexible multi-ring binding elements. The invention provides an improved adjustment feature for regulating the opening distance of a plurality of rings of multi-ring elements for binding a stack of sheets placed into the multi-ring element.
Such binding elements are known and described in U.S. Pat. No. 3,583,557. Machines for uncurling multiple rings of such a binder element are disclosed, for example, in U.S. Pat. Nos. 3,227,023, 3,125,887 and 4,645,399. In such machines, the binder element is placed against and in mesh with teeth of a comb portion. A handle is pulled by an operator which engages multiple hooks or "uncurling fingers" enmesh with the rings of the binder element to grasp the rings of the element and uncurl the rings to open them for placing a stack of sheets in position to receive the open ends of the multiple rings into corresponding holes previously punched in the stack of sheets.
According to U.S. Pat. No. 3,227,023, actuators for a slide bar which holds the uncurling fingers comes in pivotable contact with stop cams which are mounted on a shaft pivotable with respect to the machine housing and which by rotating can set a distance of uncurling.